Coinage metal (Au, Ag, Cu) ions exhibit distinct biological activities which could be harnessed to give effective therapeutic agents for anti-arithric, antimicrobial, and anti-cancer treatment.1-6 The naked M+0 ions, however, are unstable under physiological conditions and their instability such as that due to precipitation, aerobic oxidation and reduction can be circumvented by using appropriate auxiliary ligands. In literature, phosphine ligands are used to develop bioactive d10 metals compounds though they are also cytotoxic.7-9 Recent work has also witnessed new ligand systems such as N-heterocyclic carbenes. 10-13 
Thiourea ligands are well documented in coordination chemistry, and have recently been receiving an upsurge interest in the area of new metal catalysts. Nevertheless, biological studies on metal-thiourea complexes are sparse. This invention relates to coinage metal complexes of an N,N′-disubstituted cyclic thiourea which deliver significant cytotoxicties to cancer cells and in particular, gold(I) thiourea complex exhibits potent tight-binding inhibition of anticancer drug target thioredoxin reductase.